1. Field of the Invention
The present invention relates to stabilizing organic substrate materials and, more particularly, to stabilizing organic compounds and particularly photographic dye images to light.
2. Description of the Prior Art
In general, it is widely known that organic substrate materials, for example, organic dyes tend to fade or discolor by the action of light and in the fields of inks, textile dyeing color photography, etc., means of improving the light fastness of organic dyes, preventing fading or discoloring of such organic dyes, etc., have been investigated. Many methods for reducing the occurence of fading or discoloring or increasing the light fastness of these organic substrate materials have been reported. For example, U.S. Pat. No. 3,432,300 discloses that the resistance or stabilization of organic compounds such as indophenol dyes, indoaniline dyes, azo dyes, and azomethine dyes to visible light and ultraviolet rays is improved by mixing them with a phenol type compound having fused heterocyclic ring.
Generally, in the field of silver halide photographic materials, various methods are known for improving the stability of color images, that is, the images of dyes such as azomethine dyes or indoaniline dyes formed by the reaction of the oxidation product of an aromatic primary amine color developing agent and couplers as described in C. E. K. Mees and T. H. James; The Theory of the Photographic Process; Chapter 17, published in 1967 by Macmillan Co. For example, there are the hydroquinone derivatives described in U.S. Pat. Nos. 2,360,290; 2,418,613; 2,675,314; 2,701,197; 2,704,713; 2,728,659; 2,732,300; 2,735,765; 2,710,801; and 2,816,028; and U.K. Pat. No. 1,363,921, the gallic acid derivatives described in U.S. Pat. Nos. 3,457,079 and 3,069,262 and Japanese Patent Publication No. 13,496/'68, the p-alkoxyphenols described in U.S. Pat. Nos. 2,735,765 and 3,698,909, and the derivatives such as chroman and cumarin described in U.S. Pat. Nos. 3,432,300; 3,573,050; 3,574,627; 3,764,337; 3,574,626; 3,698,909 and 4,015,990. However, these compounds have an effect as a fading preventing agent or discoloring preventing agent for color images but the effect is insufficient.
Also, a method for improving the stability of organic compounds to light by using an azomethine quenching compound of which the absorption maximum is at a longer wavelength than the absorption maximum of the substrate material is described in U.K. Pat. No. 1,451,000 or U.S. Pat. No. 4,050,938 to Smith Jr. et al. However, since the azomethine quenching compound itself has deep color, the use of such a compound is disadvantageous in the point that it influences greatly on the color hue of the base material. In addition, it has also be found by the inventors that such as quenching compound adversely affects photographic speed, i.e., causes serious desensitization.
Also, the use of metal complexes for the prevention of light deterioration of polymers is described by J. P. Guillory and R. S. Becker in Journal of Polymer Science, Polym. Chem. Ed., 12, 993(1974) and By R. P. R. Ranaweera and G. Scott in Journal of Polymer Science, Polym. Lett., Ed., 13, 71(1975) and further a method of stabilizing dyes by metal complexes is described in Japanese patent Application (OPI) No. 87,649/'75 and "Research Disclosure", 15162(1976). However, since the fading prevention effect itself of these complexes is not so high and the solubility thereof in organic solvents is not high, it is difficult to add the complexes in an amount sufficient for obtaining the desired fading prevention effect. Furthermore, these complexes themselves are greatly colored and hence they have such difficulty that if a large amount of the complex is used, it gives bad influences on the color hue and the purity of the organic materials, in particular, dyes.